The invention relates to a lining for direct-current electric-arc furnace, and particularly for such a furnace having a top electrode centrally extending into said furnace, the second electrode comprising an electrically conductive, refractory brick lining provided on the inside of the furnace and a ring-shaped current conductor on its outside.
From European Printed Publication 0,422,406, a direct current electric-arc furnace has become known, in which the region receiving the melt comprises an electrically conductive, refractory brick lining. A cylindrical current conductor in the form of a copper ring is placed around this electrically conductive brick lining. Both the conductive brick lining and the copper ring together constitute the anode of said direct-current electric-arc furnace.
The brick lining consists of several layers. The layer which is in direct contact with the molten metal is formed of an electrically conductive, wear-resistant refractory material. For the purpose of smoothing the brick step, a layer of electrically conductive ramming mass is applied onto the layer serving as brick lining. This part of the brick lining is to consist e.g. of carbon magnesite.
A layer of graphite bricks which possess a much higher electrical conductivity is located beneath this layer. The thickness of the layer increases towards the outer edge and, there, corresponds to the level of the copper ring so that a favorable current conduction is ensured.
Adjacent to this layer is a layer of electrically insulating, refractory bricks which fills the entire bottom area of the furnace and ensures thermal insulation.
The electrical conductivity of the layer facing the molten bath and the agitation of the bath associated therewith cause a relatively uniform temperature distribution in the molten material. Due to the carbon content of the carbon magnesite bricks, inadvertent carburization of the molten steel may, however, occur when the melting steel has a deliberately low carbon content. If, furthermore, the layer facing the melt should be damaged due to mistakes during melting, e.g., insufficient heel or mechanical impacts from the charge or top electrode, so that the molten bath comes into direct contact with the graphite bricks, the letter may dissolve and the brick lining may be so heavily damaged that an extensive repair becomes necessary.
Considering the foregoing, it is an object of the invention to construct the hearth area of a direct-current electric-arc furnace in such a way that its resistance to wear is increased and the intrusion of carbon, especially from the central region of the hearth, into the melt is largely prevented.